For visuals and posters purchase the giant Post-it easel Pad. They're easy to write on (permanent marker will not bleed through), easy to tear off and stick most anywhere, even to eachother, and can be used again next year for the same lesson. They are about $20 at Sams Club for one tablet (25 sheets) which lasted me most of the year. Not sure how much they are at office stores.
Also become familiar with any electronic visual aide equipment in the classroom- some teachers have an LCD projector and office or other documents can be projected as a visual aide. This will also take care of some of the technology requirements in your various evaluation forms.